Similar to water-insoluble working fluid, water-soluble working fluid employed in metal working such as cutting is required to provide excellent machining performance. In addition, water-soluble working fluid must have high rotting resistance as an essential characteristic.
Conventionally, in enhancement of the rotting resistance of water-soluble working fluid, a higher alkalinity of the working fluid has been generally employed, and a variety of amine compounds such as cyclohexylamine, dicyclohexylamine, and alkanolamines have been used as alkali substances. Among them, dicyclohexylamine is particularly widely employed, since it provides less pungent odor and has high rotting resistance.
However, dicyclohexylamine has been recently registered as a class 1 chemical substance stipulated by the Pollutant Release and Transfer Register (PRTR) law, in that dicyclohexylamine possibly adversely affects human health and the ecological system. Thus, use of dicyclohexylamine is now less encouraged. Even under such circumstances, there is demand for a new amine compound substitute which enhances working performance and rotting resistance of water-soluble metal working fluid.
As new amine compound substitutes, a variety of amine compounds have been proposed. For example, Patent Document 1 discloses amine compounds having a cycloalkyl group, such as cyclohexylamine and N,N-dimethylcyclohexylamine.
Patent Document 2 discloses amine compounds having an aromatic moiety, such as 4-methoxy-2-methylaniline and N,N-dimethylbenzylamine. Patent Document 3 discloses an amine compound containing triethanolamine or the like, monoisopropanolamine or the like, and cyclohexylamine.
However, these amine compounds is inferior in performance to the aforementioned dicyclohexylamine. Therefore, at present, the purpose of the present invention; i.e., to reduce adverse effects on human health and the ecological system and to enhance rotting resistance, cannot fully be attained.